As disclosed in Patent Literature 1, for example, a conventional turbine is provided with turbine vanes that each include a vane body extending in the radial direction of the turbine and plate-like outer shroud and inner shroud provided respectively at both ends of the vane body in the extension direction. Inside the vane body, a serpentine channel meandering in the radial direction of the turbine is provided. The vane body is cooled as a cooling medium (cooling air) flows through the serpentine channel.
In the turbine of Patent Literature 1, a cooling medium having passed through the serpentine channel is guided into a space located farther on the radially inner side of the turbine than the inner shroud, and then flows out into a combustion gas path through a clearance between the inner shroud of the turbine vane and the platform of the turbine blade that are adjacent to each other in the axial direction of the turbine. Thus, combustion gas passing through the combustion gas path is prevented from entering the space located farther on the radially inner side of the turbine than the inner shroud.
The turbine vane of Patent Literature 2 has a serpentine channel formed therein and is provided with a plurality of cooling air holes on the trailing edge side of the inner shroud. The turbine vane of Patent Literature 2 uses a part of cooling air to cool the trailing edge of the inner shroud.
FIG. 13 to FIG. 15 show one example of a structure for cooling the trailing edge side of the inner shroud in a conventional turbine vane. As shown in FIG. 13, cooling air supplied from the outer shroud (not shown) of a turbine vane 3A enters a serpentine channel 30 and cools a vane body 21. Thereafter, the cooling air flows into a most-downstream main channel 31B that is located farthest on the side of a trailing edge end 21B of the vane body 21 in the serpentine channel 30. The cooling air flowing through the most-downstream main channel 31B convectively cools the trailing edge portion of the vane body 21 while being discharged from the trailing edge end 21B of the vane body 21 into combustion gas.
On the other hand, a cavity CB is disposed on the radially inner side of the inner shroud 22, and cooling air is supplied from the outer shroud into the cavity CB. As shown in FIG. 15, a cooling path 70 that has one end, a first end, communicating with the cavity CB and the other end, a second end, open at the downstream end of the inner shroud 22 in the turbine axial direction is formed on the trailing edge side of the inner shroud 22. The cooling path 70 is formed along the direction of combustion gas flow. The plurality of cooling paths 70 are arrayed in the circumferential direction of the inner shroud 22. The array of the plurality of cooling paths 70 mainly cools the trailing edge side of the inner shroud 22.
As shown in FIG. 14, at the downstream end of the most-downstream main channel 31B located on the most downstream side of the serpentine channel 30, the serpentine channel 30 is connected to a terminal channel 31C formed inside the inner shroud 22. An outflow path 29 that provides communication between the terminal channel 31C and a disc cavity CD located on the downstream side from the cavity CB in the turbine axial direction is provided on the downstream side from the terminal channel 31C. The opening of the terminal channel 31C that is open in an upstream-side end face 26a of a rib 26 of the inner shroud 22 is closed with a cover 26b etc. With the outflow path 29 provided, cooling air flowing inside the inner shroud 22 cools the inner shroud 22 in the vicinity of the terminal channel 31C of the serpentine channel 30, and at the same time is used as a part of purge air for the disc cavity CD.